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Performing X-ray stress measurement by a new method called the cosα method is spreading in Japan. The cosα method is characterized in that the entire diffraction ring is used and analysed. As a result, the measurement speed is fast, and the device can be downsized. On the other hand, the conventional sin2ψ method requires precise measurement of diffracted X-rays at several X-ray incident angles, which increases the measurement time and the size of the device. In addition, since only a small part of the diffraction ring generated during the X-ray irradiation is used, some of the information on the diffraction ring cannot be used so it is a wasteful method. In 2012, cosα method equipment was released in Japan. Since then, cosα method X-ray stress measurements have been performed at more than 300 facilities. In response to this situation, the Japan Society for Nondestructive Inspection (JSNDI) together with public and private institutions established a study group on the cosα method in 2014, and examined the cosα method and its appropriate use. In this paper, we report the results of this study group.

Currently, the sin2ψ method is established as an effective technique as how to measure the residual stress state of metal materials non-destructively by X-ray diffraction. In recent years, new X-ray stress measurements with two-dimensional detector are developed and spreading in the world. There is the cosα method as one of the new techniques. However, the research about the statistical errors in the method continues. The measurement theory of the cos α method is reviewed on the triaxial stress state. The triaxial stress analysis by the method is examined and discussed from a viewpoint of the derived errors for the determination.

This study addresses the finished surface quality of cemented tungsten carbide obtained via direct cutting with a diamond-coated carbide end mill under ultrasmall feed rates. The surface appearance, composition distribution, profile, roughness, residual stress, and transverse rupture strength were experimentally investigated. The finished surfaces obtained via electric discharge machining with two types of machining conditions and mechanical polishing processes were also evaluated to compare the surface quality. Two types of cemented tungsten carbide materials, TAS VC-70 and VM-40, were applied as the workpiece materials. A mirror surface can be obtained via direct cutting and mechanical polishing with both materials. The microstructure morphologies of the finished surface obtained via direct cutting were different from those obtained via mechanical polishing. In the case of VC-70 which has larger tungsten carbide grain size and higher cobalt content, the flat cross-section of the tungsten carbide grain under ductile mode cutting was conspicuous in direct cutting under small feed rate and depth of cut. In contrast, an extremely thin layer composed of fine grains of tungsten carbide and cobalt was observed on the finished surface in direct cutting under comparatively large feed rate and depth of cut. The surface roughness and profile of the finished surface resulting from direct cutting were comparatively rougher than those resulting from mechanical polishing, although the finished surface was significantly smoother than that resulting from electric discharge machining. The residual stress of the subsurface obtained via direct cutting showed larger compressive stress than that obtained via electric discharge machining and mechanical polishing under all cutting conditions and materials. Moreover, satisfactory transverse rupture strength can be obtained via direct cutting in both materials compared with other processes, and two times more transverse rupture strength can be achieved via direct cutting compared with the case of electric discharge machining in VM-40 cutting.

The burnished surface quality of a Ni-based alloy was investigated. For this, we developed and utilized a sliding burnishing process with an active rotary diamond-like carbon-coated carbide tool. Two kinds of Ni-based alloys subjected to solution heat and aging heat treatments were used as workpiece materials. The burnished surface quality was evaluated based on the roughness and profile of the surface, hardness, and the microstructure of the subsurface, residual stress, and full-width at half maximum based on X-ray analysis, and bending property of the testpiece. The preliminary surface, which was finished by filing, was also evaluated for comparison. A smooth-finished surface of approximately Ra = 0.1 μm or less was obtained by the burnishing process in both materials. The subsurface hardness of the solution heat-treated material was increased by the burnishing process, and it was also observed to increase with the thrust force as a burnishing condition, while the influence of the burnishing process on the subsurface hardness at a depth of 20 μm or more from the surface was hardly observed in the aging heat-treated sample. A large compressive residual stress and the full-width at half maximum can be obtained for the burnished surface. Based on the three-point bending test using the solution heat-treated material, the yield load transitioned from the elastic to the plastic region increased and the bending strength also clearly increased due to the burnishing process for a thrust force of 100 N. The developed sliding burnishing process with diamond-like carbon-coated carbide tool can yield a high-quality surface with low roughness, high hardness, and large compressive residual stress of Ni-based alloys based on solution heat treatment and aging heat treatment, respectively.

Rolling contact fatigue (RCF) testings of thrust ball bearing under boundary lubrication condition (low lambda condition) are conducted while changing test conditions of load, rotational speed and combination of surface roughnesses for bearing component parts. The RCF test results and measurements of surface roughnesses of before and after the tests show that the raceway surface with larger roughness promotes the surface initiated failure of the other component. In addition, they demonstrate that the behavior of change in surface roughness during rolling contact depends on the test conditions and influences RCF life accordingly. These results suggest that RCF life of rolling bearing used under low lambda conditions should be estimated considering not only analytical relationship between repeated stress in subsurface and surface roughness during RCF, but also experimental database of the running-in behavior depending on RCF conditions.

In this study, a silicon on insulator (SOI) pixel detector was applied to the X-ray stress measurement of steel. Two integration-type SOI pixel sensor chips, INTPIX4, were used to measure a Debye–Scherrer ring. Stresses were determined through data analysis of the ring and using the cos( α ) method. To examine the validity of the system for practical use, stress measurements were conducted at several points on a steel sample manufactured with welding. The sample consisted of various surfaces with crystallographic conditions, such as coarse-grains on welding beads, crystal grains covered by oxide films, and crystallographic textured grains. The results obtained using the SOI pixel detector were compared with those obtained using an image plate.

At current industrial sites for the manufacturing of fabricated metal products, a complete nondestructive, noncontact inspection of the residual stress and hardness is required. However, the conventional Debye-ring measurement system is used only for sampling inspection or research because the measurement time is long. Therefore, we have developed a high-speed Debye-ring measurement system using an integration-type silicon-on-insulator (SOI) pixel detector (INTPIX4) that can evaluate material characteristics for industrial purposes. The INTPIX4 is an X-ray imager with 832 × 512 pixels, where the size of each pixel is 17 μ m x 17 μ m . By using an SOI evaluation board with SiTCP 2 (SEABAS2), it is possible to measure Debye-rings up to 45 times in 1 s. The developed system is a compact and high-speed Debye-ring measurement system that uses two INTPIX4 detectors and a compact high-power X-ray tube. We evaluate the performance of the system.

The sin2 ψ method [1] is conventionally used well as how to measure non-destructively the residual strain and stress states of polycrystalline materials by X-ray diffraction. In the conventional method, there are Dölle-Hauk method [2] and Winholz-Cohen least squares analysis [3] as the determinations of the strain and stress states for limiting the influence of measurement errors. Many researches are made about the statistical error in those methods. In recent years, use of the X-ray stress measurements with two-dimensional detector from the conventional method is spreading. One of the measurements is called the cos α method. The measurement errors have attracted a great deal of attention for users as the spreads. Therefore, the basic equations and determinations of the strain and stress states are examined. The confidence intervals of measured stress by the cos α method. The research and development is performed for the the cos α method which took the influence of measurement errors into consideration.

In this study, the diffraction rings were measured point by point all over the head of rail sample which was used in service, and shearing stresses with respect to the depth direction were determined using the generalized cosα method. The full width at half maximum was also estimated from the diffraction ring.

In comparison to conventional discrete-variable (DV) quantum key distribution (QKD), continuous-variable (CV) QKD with homodyne/heterodyne measurements has distinct advantages of lower-cost implementation and affinity to wavelength division multiplexing. On the other hand, its continuous nature makes it harder to accommodate to practical signal processing, which is always discretized, leading to lack of complete security proofs so far. Here we propose a tight and robust method of estimating fidelity of an optical pulse to a coherent state via heterodyne measurements. We then construct a binary phase modulated CV QKD protocol and prove its security in the finite-key-size regime against general coherent attacks, based on proof techniques of DV QKD. Such a complete security proof achieves a significant milestone in exploiting the benefits of CV QKD., Comment: 12 pages, 4 figures

INTPIX4NA is an integration-type silicon-on-insulator pixel detector. This detector has a 14.1 x 8.7 mm^2 sensitive area, 425,984 (832 column x 512 row matrix) pixels and the pixel size is 17 x 17 um^2. This detector was developed for residual stress measurement using X-rays (the cos alpha method). The performance of INTPIX4NA was tested with the synchrotron beamlines of the Photon Factory (KEK), and the following results were obtained. The modulation transfer function, the index of the spatial resolution, was more than 50% at the Nyquist frequency (29.4 cycle/mm). The energy resolution analyzed from the collected charge counts is 35.3%--46.2% at 5.415 keV, 21.7%--35.6% at 8 keV, and 15.7%--19.4% at 12 keV. The X-ray signal can be separated from the noise even at a low energy of 5.415 keV at room temperature (approximately 25--27 degree Celsius). The maximum frame rate at which the signal quality can be maintained is 153 fps in the current measurement system. These results satisfy the required performance in the air and at room temperature (approximately 25--27 degree Celsius) condition that is assumed for the environment of the residual stress measurement., Comment: Accepted for publication at JINST (2022/01/14 Typo correction ver.)

The eddy current magnetic signature (EC-MS) method is a relatively new method used to evaluate the residual stresses of ferromagnetic steels with higher sensitivity than other magnetic techniques. In this study, the effects of mechanical polishing and the ferrite–pearlite structure on the shape of the EC-MS signal were investigated in two experiments to clarify the effect of compressive residual stress on the EC-MS signal shape. In the first experiment, the work-hardened layers of the specimens were removed by electrolytic polishing and the EC-MS signals of the specimens were investigated. The second experiment involved the EC-MS measurements of materials with different pearlite contents, i.e., low-carbon steel with 0.17% and 0.27% carbon and pure iron. Specimens with different residual strains were prepared using a tensile test apparatus and their EC-MS signals were compared. In both experiments, the residual stresses acting on the specimens were measured adopting X-ray diffraction. The results reveal that the non-anisotropic compressive residual stress acting on the specimen surface changed the EC-MS signal in an anti-clockwise manner while the unidirectional compressive residual stress inside the specimen changed the EC-MS signal in a clockwise manner.

To guarantee the security of quantum key distribution (QKD), several assumptions on light sources must be satisfied. For example, each random bit information is precisely encoded on an optical pulse and the photon-number probability distribution of the pulse is exactly known. Unfortunately, however, it is hard to check if all the assumptions are really met in practice, and it is preferable that we have minimal number of device assumptions. In this paper, we adopt the differential-phase-shift (DPS) QKD protocol and drastically mitigate the requirements on light sources. Specifically, we only assume the independence among emitted pulses, the independence of the vacuum emission probability from a chosen bit, and upper bounds on the tail distribution function of the total photon number in a single block of pulses for single, two and three photons. Remarkably, no other detailed characterizations, such as the amount of phase modulation, are required. Our security proof significantly relaxes demands for light sources, which paves a route to guarantee implementation security with simple verification of the devices., 10 pages, 2 figures

Blind quantum computation is a scheme that adds unconditional security to cloud quantum computation. In the protocol proposed by Broadbent, Fitzsimons, and Kashefi, the ability to prepare and transmit a single qubit is required for a user (client) who uses a quantum computer remotely. In case a weak coherent pulse is used as a pseudo single photon source, however, we must introduce decoy states, owing to the inherent risk of transmitting multiple photon. In this study, we demonstrate that by using a heralded single photon source and a probabilistic photon number resolving detector, we can gain a higher blind state generation efficiency and longer access distance, owing to noise reduction on account of the heralding signal., Comment: 15 pages, 6 figures

The random number generators (RNGs) are an indispensable tool in cryptography. Of various types of RNG method, those using radiations from nuclear decays (radioactive RNG) has a relatively long history but their security has never been discussed rigorously in the literature. In this paper we propose a new method of the radioactive RNG that admits a simple and rigorous proof of security. The security proof is made possible here by exploiting the parity (space inversion) symmetry arising in the device, which has previously been unfocused but is generically available for a nuclide which decays by parity-conserving interactions., Comment: 8 pages, 4 figures

Among many quantum key distribution (QKD) protocols, the round-robin differential phase shift (RRDPS) protocol is unique in that it can upper-bound the amount of the information leakage without monitoring the signal disturbance. To expedite implementation of the protocol, however, the number of pulses forming a single block should be kept small, which significantly decreases the key rates in the original security proof. In the present paper, we refine the security proof of the RRDPS protocol in the finite-sized regime and achieve a tighter estimation for the information leakage without changing the original experimental setups. As a consequence, we obtain better key rates in both asymptotic and finite-sized cases while keeping the preferable features of the protocol, such as omission of phase randomization., 25 pages, 5 figures

In a previous study, the authors introduced a new nondestructive method to measure stress with a two-dimensional X-ray diffraction image. This method was tested on a carbon steel specimen. To apply...

A technique to improve X-ray stress measurement using Debye–Scherrer rings is reported. In previous work, a Fourier-series-based generalization of the cosα method was proposed, which can measure the stress from a Debye–Scherrer ring. That technique and the cosα method have difficulties in determining the stress when the grain size of the specimen is relatively large and the Debye–Scherrer ring is grainy. To cope with this problem, in-plane averaging has been used to improve the cosα method when measuring coarse-grained specimens. In this study, Fourier series analysis is incorporated with in-plane averaging and it is explained how in-plane averaging improves the stress measurement. Furthermore, the validity of the new technique is demonstrated by measuring the stress of a carbon steel specimen.

A fundamental study was conducted on the effectiveness of a silicon-on-insulator (SOI) pixel detector for industrial applications. In this study, we developed a measurement system for X-ray tri-axial stress analysis by using an INTPIX4, an integrated SOI pixel detector developed by Arai et al. This system measured the diffraction ring diffracted backward from the polycrystalline sample by using a CrK α characteristic X-ray, and performed a tri-axial residual stress analysis by applying the generalised cos α method. To verify this measurement system, we measured the residual stress of a rail used in service and examined the state of rolling contact fatigue due to contact with wheels. In this measurement, diffraction rings generated from 211 diffraction lines of the ferrite phase in the rail steel were measured. The results of this system were compared with those obtained from a commercial device using an image plate (IP). As a result, this measurement system was found to be able to effectively measure the tri-axial residual stress component 30 times faster than the commercial device, and proved to be promising for rail inspection.

The technology for evaluation of metal materials encompasses machine parts and structures. Residual stress is one indicator used for evaluating the strength and stiffness of metal materials. X-ray residual stress measurement is a non-destructive, non-contact, and precise method in various residual stress measurement methods. This method is used only for research purposes because of its long measurement time and large device size. Therefore, we developed a small, high-speed X-ray residual stress measurement device with a charge-integration-type silicon-on-insulator (SOI) pixel detector, INTPIX4, for industrial use. Previous studies have shown that residual stress can be measured in less than 1 s by using a measurement device with an SOI pixel detector. In this study, we report a more detailed specification of the measurement device and consider its availability for metal material evaluation.

Residual stress is an important factor governing evaluating and controlling the quality of metal materials in industrial products. X-ray measurements provide one of the most effective means of evaluating residual stress without destruction. In such measurements, the effects of residual stress on the crystal structure can be observed through the Debye ring deformation. In previous studies, we developed a residual stress measurement system based on the c o s α method, using a two-dimensional (2D) silicon-on-insulator pixel (SOIPIX) detector known as INTPIX4. In a typical laboratory setup, this system requires only 1 s to measure a specified point. This is drastically faster than the conventional system based on the s i n 2 ψ method, which requires more than 10 min, and the c o s α -based system using an imaging plate, which requires 1 min. Compared to other systems, it can evaluate the 2D distribution of residual stress faster and provide more detailed information for evaluating materials. We first attempted to measure the 2D distribution in a laboratory setup with a Cr X-ray tube (Cr K α 5.4 keV) and obtained satisfactory results. We subsequently took measurements using synchrotron monochromatic X-rays to determine the fine accuracy and fine sampling pitch distribution. In this paper, we report the results of the initial synchrotron experiment, including the residual stress distribution of the standard specimen obtained by the first prototype setup. Furthermore, we compare the synchrotron measurements with those from the laboratory.

Cold spray (CS) residual stress was measured by the X-ray diffraction (XRD) and contour methods. The residual stress components SX and SY, perpendicular to the thickness, have similar distributions and approximately equal magnitudes. Both are compressive on the deposited surface and become tensile inside the structure. An advanced simulation model based on the arbitrary Lagrangian–Eulerian (ALE) method was developed to investigate the residual stress distributions in a single CS microparticle and multi-layer CS microparticles and reveal the formation mechanism. The residual stress components SX and SY predicted by the proposed simulation model have the same distribution as shown by the measurements, i.e., compressive on the surface and tensile inside. As the number of deposition layers increases, the position of maximum tensile stress moves from the substrate to the deposited layers. The residual stress component SZ in the direction of the deposition thickness shows alternate tensile and compressive distributions in the transverse direction, which is quite different from that of the transverse component. The formation of CS residual stress is mainly affected by three aspects: the collisions among microparticles, the interactions between microparticles in the same layer, and interactions between microparticles in different layers. The present work provides a guideline for effectively tailoring the residual stress in CS parts and thereby improving the fatigue lifetime.

Quantum key distribution (QKD) allows two distant parties to share secret keys with the proven security even in the presence of an eavesdropper with unbounded computational power. Recently, GHz-clock decoy QKD systems have been realized by employing ultrafast optical communication devices. However, security loopholes of high-speed systems have not been fully explored yet. Here we point out a security loophole at the transmitter of the GHz-clock QKD, which is a common problem in high-speed QKD systems using practical band-width limited devices. We experimentally observe the inter-pulse intensity correlation and modulation pattern-dependent intensity deviation in a practical high-speed QKD system. Such correlation violates the assumption of most security theories. We also provide its countermeasure which does not require significant changes of hardware and can generate keys secure over 100 km fiber transmission. Our countermeasure is simple, effective and applicable to wide range of high-speed QKD systems, and thus paves the way to realize ultrafast and security-certified commercial QKD systems. A potential security loophole and its countermeasure have been discovered in practical implementations of high-speed quantum key distribution (QKD). Ken-ichiro Yoshino from NEC corporation and a team of researchers from Japan investigated the intensity fluctuations of optical pulses in a GHz-clocked QKD system, revealing that the limited bandwidth of the ultrafast optical transmitter’s electronics generates deviations from the ideal signal. These perturbations have been shown to carry signatures of previous modulation patterns - effectively introducing correlations between individual pulses. As the strength of QKD relies on its proof-of-principle security, which in many cases is derived under the assumption of independent pulses, these correlations constitute a loophole that might compromise the whole protocol. Fortunately, the researchers developed two countermeasures: pattern sifting and alternate key distillation, which recover security and do not impact performances too severely.

A technique to improve the stress measurement from a Debye–Scherrer ring (D–S ring) is reported. In a previous work, the authors reported a technique to calculate stress from the Fourier series of the normal strain of a D–S ring. That technique, similar to the cosα method that came before it, is inaccurate when the grain size of the specimen is relatively large. To cope with this problem, the authors propose using the oscillation of the X-ray incident angle. The present study demonstrates this technique to improve the stress measurement.