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widely‐used hypoelastic model for four well‐known objective stress rates under a four‐phase stress cycle associated with axial tension and/or torsion of thin‐walled cylindrical tubes. Here, two kinds of models based upon the Cauchy stress and the Kirchhoff stress will be treated. The reduced systems of differential equations of these rate constitutive equations are derived and studied for Jaumann, Green‐ Naghdi, logarithmic and Truesdell stress rates, separately. Analytical solutions in some cases and numerical solutions in all cases are obtained using these reduced systems. Comparisons between the residual deformations are made for different cases. It may be seen that only the logarithmic stress rate results in no residual deformation. In particular, results indicate that Green‐Naghdi rate would generate unexpected residual deformation effect that is essentially different from that resulting from Jaumann rate. On the other hand, it is realized that this study accomplishes an alternative, direct proof for the nonintegrability problem of Truesdell’s hypoelastic rate equation with classical stress rates. This problem has been first treated successfully by Simo and Pister in 1984 using Bernstein’s integrability conditions. However, such treatment needs to cope with a coupled system of nonlinear partial differential equations in Cauchy stress. Here, a different idea is used. It is noted that every integrable hypoelastic equation is just an equivalent rate form of an elastic equation and hence should produce no residual deformations under every possible stress cycle. Accordingly, a hypoelastic model with a stress rate has to be non‐integrable, whenever a stress cycle can be found under which this model generates residual deformation. According to this idea of reductio ad absurdum, a well‐designed stress cycle is introduced and the corresponding residual deformations are calculated. Unlike the treatment of Bernstein’s integrability conditions, it may be a simple and straightforward matter to calculate the final deformations for a given stress cycle. This has been done in this study for several well‐known stress rates.

PurposeThe purpose of this paper is to investigate a new approach for making a bio‐based adhesive from a new resource, rice bran (RB) adhesive.Design/methodology/approachRB solution was prepared and its pHs were adjusted to either 8.5‐9.0 or 10.0‐10.5. The solid content of slurry was controlled at ≈18 per cent and then gelatinised in a water bath shaker at 60°C for 2 h or at 100°C for 1 h. The bonding strength of RB adhesive was determined by testing the strength of three‐layer plywood. A differential scanning calorimeter (DSC) was used for detecting the reaction energy and curing temperature. According to the DSC analysis, hot pressing at three temperatures was performed to select the best bonding conditions. Then, a two level split‐plot design was used to determine the effects of gelatinisation and pH on the bonding strength of RB adhesive. Thus, the formulation of RB adhesive was optimised. In order to improve the water resistance of RB adhesive, toluene diisocyanate (TDI) was used as a cross linking agent.FindingsIn the study reported here, a RB adhesive was developed by alkaline modification. Very high pH was not necessary, when RB adhesive with pH 10.0‐10.5 was gelatinised at 100°C for 1 h, its bonding strength was significantly lower than pH 8.5‐9.0 gelatinised at 60°C for 2 h. Water resistance of RB adhesive improved significantly when TDI was added as a cross linking agent. Compared to pure RB adhesive, the RB‐TDI mixed adhesive started curing at a higher temperature. For RB adhesive curing, 130°C was a suitable hot pressing temperature.Research limitations/implicationsThough the RB adhesive developed had a good bonding strength, its water resistance and dark colour was not satisfactory, which risks discolour of light colour wood. Further study is needed to solve this problem.Practical implicationsThe approach provided a bio‐adhesive with good bonding strength, reasonable working life, and without formaldehyde emission. Based on further study, RB adhesive could be considered a promising alternate adhesive in many applications such as paper board bonding and plywood.Originality/valueIt provided a potential way to utilise by‐product of agriculture, RB as industrial raw material. This will do farmers a great favour. Meanwhile, the modified RB adhesive is promising to partly or completely replace urea formaldehyde resin that mainly used in wood industry, avoiding formaldehyde emission and reducing the dependence on petroleum products.

PurposeTo investigate a new approach for making soy‐based adhesive having appropriate properties for potential application in wood industry.Design/methodology/approachThree chemicals were used for modifying protein contained in soy flour. According to orthogonal experiment design, nine soy‐based adhesives were prepared. Shearing strength of plywood bonded with these adhesives was measured to evaluate the bonding strength of nine formulas. Based on statistic analysis, the main effect factor and an optimised formula were determined. Further investigation on the modification effect to protein molecule was conducted by Fourier Transform Infrared Spectroscopy. In order to facilitate practical application, the viscosity of optimum formula adhesive was measured to determine possible working life. Three additives were added to optimise formula for reducing mould growth.FindingsBased on soy‐flour mass, the best combination of lime milk, sodium hydroxide (NaOH) and sodium silicate was 10, 2, and 20 per cent, respectively. NaOH was considered the main effect factor on bonding strength, and sodium silicate was of the second importance. The viscosity of the optimised adhesive changed lightly in 2 h, and significantly increased from 2 to 4 h. However, it still could spread on veneer, which indicated a reasonable working life for practical application. Based on soy flour mass, when 0.5 per cent sodium benzoate or 25 per cent phenol formaldehyde was added, mould growth could be restrained after early stage.Research limitations/implicationsThough the studied soy‐based adhesive had a good bonding strength and comparative water resistance, its pH was a little too high, which may cause risks of discolour of light coloured wood. Further study is needed to solve this problem.Practical implicationsThe approach provided a bio‐adhesive with good bonding strength, comparative water resistance, reasonable working life, and without formaldehyde emission. Soy‐based adhesive is considered a promising alternate adhesive in wood industry and other applications because of the above mentioned advantages.Originality/valueIt provided a potential way to utilise by‐product of agriculture, soy‐flour, as industrial raw material. This will benefit farmers significantly. Meanwhile, the modified soy‐based adhesive is promising to partly or completely replace urea formaldehyde resin that are mainly used in wood industry, avoiding formaldehyde emission and reducing the dependence on petroleum products.