Search

Panic buying has been globally observed, leading to substantial stock-outs and supply chain disruptions, thus inducing additional panic buying. Regarding panic buying behavior as an intuitive over-protective measure during the strict lockdown and seal-off management in China, this study presented a synthetic conceptual model by integrating the protective action decision model (PADM). We examined inductively the relationships among media exposure, cognitive-affective risk perception, stakeholder perception, protective perception, and panic buying behavior using a survey of 517 participants who experienced panic buying during the Omicron epidemic in China. Results suggest that traditional media exposure could attenuate people’s affective risk perception, whereas social media exposure increases the degree of cognitive and affective aspects of risk perception. Furthermore, we detect that cognitive and affective risk perceptions positively affect people’s panic-buying behaviors. The effects of stakeholder and protective perceptions on panic buying were also examined.

In a new era of mass entrepreneurship and innovation, Yanjiang Street in Jiangbei new district of Nanjing city actively introduces private capital and jointly builds Dingmeng E-commerce Pioneer Park with enterprises. The two sides respectively input government services and supporting resources, enterprise innovation and driving resources, to establish the first e-commerce pioneer park in the whole region, and gather social innovation forces and innovative talents, fully stimulate the entrepreneurship and innovation vitality of enterprises in the incubation base. In this process, both the government and enterprises gather strength and focus on the cultivation and reconstruction of excellent Internet brands. At present, this model has achieved good stage results and has been widely recognized by all sectors of society.

Incremental sheet metal flanging is efficient and cost-effective in prototyping and low-volume production. However, how the sheet metal fails and how the overall formability is enhanced during incremental sheet flanging are still not well understood. This study attempts to provide an updated level of understanding for the deformation mechanics in fabricating a clover hole-flange with complex in-plane curvatures by double-sided incremental forming. Compared with traditional flanging methods, higher formability has been achieved for both stretch flanging and shrink flanging on a single part. Additionally, numerical simulation is conducted complementarily to reveal the strain evolution, based on which failure modes and reasons are analyzed. Moreover, DMV (Donell–Mushtari–Vlasov) equations are employed to analytically study the shrink flanging process. The investigations lead to the conclusions that meridional tension has positive effect in improving the formability during shrink flanging, while an adverse effect is found in the formability during stretch flanging.

Woven composites are considered as a promising material choice for lightweight applications. An improved non-orthogonal material model that can decouple the strong tension and weak shear behavior of the woven composite under large shear deformation is proposed for simulating the preforming of woven composites. The tension, shear and compression moduli in the model are calibrated using the tension, bias-extension and bending experiments, respectively. The interaction between the composite layers is characterized by a sliding test. The newly developed material model is implemented in the commercial finite element software LS-DYNA® and validated by a double dome study.

The success of a toolpath in double-sided incremental forming (DSIF) is strongly related to the specified tool gap. It is hypothesized in this work that maintained contact between tools and the sheet can improve the distribution of sheet thickness and hence, improve material formability and prevent premature fracture. Simulation and experimental studies reveal that thickness prediction models solely dependent on the local wall angle are inadequate for general part geometries. A ‘Shamrock’ geometry is proposed leading to the development of a novel improved thickness correction model that incorporates wall angle, in-plane curvature, and tool direction.

In this paper, dynamic spherical cavity expansion model is developed for rate-dependent concrete material described by modified Drucker-Prager Cap plasticity model incorporated with size effect. Penetration resistance components are computed accordingly with static resistance dependent on projectile diameter scale. Saturated region is introduced to investigate the response of concrete target under high impacting velocity. The validation of the proposed model is conducted by modelling a rigid projectile with full-scale and 1/10-scale diameter penetrating a semi-infinite concrete target. Depth of penetration numerically obtained is also compared with some widely recognized empirical penetration formulae, and better agreement is achieved by the proposed model for penetration tests with various striking velocities.

It is essential to accurately describe the large shear behavior of woven fabrics in the composite preforming process. An analytical model is proposed to describe the shear behavior of fabrics with different weave patterns, in which tension-shear coupling is considered. The coupling is involved in two parts, the friction between overlapped yarns and the in-plane transverse compression between two parallel yarns. By introducing the concept of inflection points of a yarn, the model is applicable for fabrics with different weave patterns. The analytical model is validated by biaxial tension-shear experiments. A parametric study is conducted to investigate the effects of external load, yarn geometry, and weave structure on the large shear behavior of fabrics. The developed model can reveal the physical mechanism of tension-shear coupling of woven fabrics. Moreover, the model has a high computational efficiency due to its explicit expressions, thus benefiting the material design process.

This paper investigates the application of bioinspired serrated cutting edges in tissue cutting by biopsy punches (BPs) to reduce the insertion force. BPs are frequently used as a diagnostic tool in many minimally invasive procedures, for both tissue extraction and the delivery of medical fluids. The proposed work is inspired by the mosquito's maxilla that features microserrations on its cutting edges with the purpose of painlessly puncturing the human skin. The objective of this paper is to study the application of maxillalike microserrations on commercial BPs. The fundamental goal is the minimization of the puncture force at the BP tip during insertion procedures. Microserrations were created on the cutting edge by using a picosecond laser while cutting tests were implemented on a customized testbed on phantom tissue. A reduction of 20–30% in the insertion forces has been achieved with microserrated punches with different texture depths encouraging, thereby, further studies and applications in biomedical devices. Three-dimensional (3D) and two-dimensional (2D) finite element simulations were also developed to investigate the impact of microserrated cutting edges on the stresses in the contact area during soft tissue cutting.

Double-sided incremental forming (DSIF) is a subcategory of general incremental sheet forming (ISF), and uses tools above and below a sheet of metal to squeeze and bend the material into freeform geometries. Due to the relatively slow nature of the DSIF process and the necessity to capture through-thickness mechanics, typical finite element simulations require weeks or even months to finish. In this study, an explicit finite element simulation framework was developed in LS-DYNA using fully integrated shell elements in an effort to lower the typical simulation time while still capturing the mechanics of DSIF. The tool speed, mesh size, element type, and amount of mass scaling were each varied in order to achieve a fast simulation with minimal sacrifice regarding accuracy. Using 8 CPUs, the finalized DSIF model simulated a funnel toolpath in just one day. Experimental strains, forces, and overall geometry were used to verify the simulation. While the simulation forces tended to be high, the trends were still well captured by the simulation model. The thickness and in-plane strains were found to be in good agreement with the experiments.

Double-sided incremental forming (DSIF) is a relatively new dieless forming process which uses two hemispherical ended tools, one on each side of the sheet, moving along a predefined trajectory to locally deform a peripherally clamped sheet of metal. DSIF provides greater process flexibility, higher formability, and eliminates the tooling cost when compared to conventional sheet forming processes. While DSIF provides much improved geometric accuracy compared to other incremental forming processes, current toolpath planning strategies suffer from long forming times. A novel mixed double-sided incremental forming (MDSIF) toolpath strategy is proposed in the present study. It simultaneously reduces the total forming time by half while preserving the best currently achievable geometric accuracy. The effect of the forming parameters, i.e., of the incremental depth and of tool positioning on the geometric accuracy of the parts formed with MDSIF was investigated and compared to those formed by traditional DSIF strategies.

Incremental sheet forming (ISF) has gained much attention in the low volume production and rapid prototyping fields due to its inherent flexibility, low-overhead cost, and die-less nature. However, the geometric inaccuracy of the final achievable parts hinders this process from becoming commercially viable. One of the major sources of geometric inaccuracy is springback, which predominately occurs when the formed sheet metal is unloaded by the forming tools and released from the clamps. This paper focuses on the latter case. A practical annealing method that does not rely on complicated setups and geometry-specific compensation algorithms is proposed to reduce the springback that occurs after the unclamping process. Two clamping devices were developed, which have been demonstrated to significantly reduce the amount of springback. The capability of reducing springback by the proposed method and its potential of integrating it with other geometric accuracy improvement methods will enhance the ISF process towards future industrial applications.