The peel test is a popular test method for measuring the peeling energy between flexible laminates. However, when plastic deformation occurs in the peel arm(s) the determination of the true adhesive fracture energy, G c , from the measured peel load is far from straightforward.Two different methods of approaching this problem have been reported in recently published papers, namely: (a) a simple linear-elastic stiffness approach, and (b) a critical, limiting maximum stress, σ max , approach. In the present paper, these approaches will be explored and contrasted. Our aims include trying to identify the physical meaning, if any, of the parameter σ max and deciding which is the better approach for defining fracture, when suitable definitive experiments are undertaken.Keywords: cohesive zone models; fracture mechanics; laminates; peel tests; plastic deformation. 2 INTRODUCTIONThe peel test is a popular test method for measuring the peeling energy between flexible laminates [e.g. [1][2][3]. The simple single-arm form is shown in Figure 1a and the 'T-peel' variant is illustrated in Figure 1b. For the former test method, the total energy input, G, is related to the applied steady-state peel load, P, the width, b, of the specimen and the peel angle, θ, by:(1 cos )and for the 'T-peel' we essentially have two such specimens 'back-to-back', each with 2 π θ = , such that:This value of G includes the adhesive fracture energy, G c , and any plastic work done in bending the peeling arm(s). The value of the adhesive fracture energy, G c , is assumed to be a 'characteristic' property of the adhesive, or interface, and ideally independent of geometrical details of the peel test such as the thickness, h, of the peel arm and the peel angle, θ.However, the value of G c would, of course, be expected to typically be dependent upon the test rate and temperature, since we are dealing with viscoelastic materials.When only elastic deformation occurs in the peeling arm there is no energy dissipation, so that c G G = . However, in many cases, there is a rather complex bending and unbending process, as shown, for 2 π θ = in Figure 2a where the peeling arm is initially bent and then gradually straightened as the peeling proceeds. A schematic diagram of the bending moment, M/b, per unit width in the peel arm and the inverse of the local radius, 1/R, of curvature at the peel front is shown in Figure 2b and the area under the curve is the plasticenergy dissipated in bending. When a non-work hardening material is used for the peel arm, the moments tend to the plastic limit:3 where M p is the fully plastic moment, y σ is the yield stress and h is the thickness of the peel arm, and for large values of the plastic-energy dissipation:A crucial factor in the analysis is the root rotation, o θ , illustrated in Figure 3. This arises from stretching of the substrate peeling arm before it debonds and reduces the plastic work done such that the proportion of G going into plastic work,Considering now only the 90° peel test, and assuming o θ to be small, then...

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Thermal processing is an economical and efficient way of manufacturing polymeric products. However, it suffers from an important side effect that may considerably affect product performance: during non-uniform cooling to room temperature, strains become 'frozen in' the material. These frozen in strains lead to undesirable distortions and residual stresses within the final product. This work is concerned with cast filled PMMA plates for domestic applications. In a typical casting process, the material is first polymerised at a high temperature and then cooled to the ambient temperature. After cooling, the plate has distorted to an extent dependent on the cooling conditions.A method has been developed for quantitative prediction of the distortions and consequent residual stresses caused by non-uniform solidification. A 'residual' temperature field is introduced, which provides the relationship between the thermal history and frozen in strains. When applied as an actual temperature distribution, it results in distortions and residual stresses. Laboratory tests indicative of the actual casting process validated the frozen in strain model. Preheated plates were cooled in a controlled environment while temperatures were recorded at a number of locations on the plate surfaces. The measured temperature histories were then used in the numerical prediction of the residual temperature field. Experimental and numerically predicted distorted shapes agree very well.

High speed steel (HSS) is a very important industrial tool material and has been constantly improved for different wear resistance applications and cutting tools, i.e. drills, milling cutters, hobs and for the cutting tools in which the economical cutting speed is too low for choosing the carbide tools. The properties of HSS depend significantly on the parameters of the conducted heat treatment. In this paper, the influence of deep cryogenic treatment in combination with nitriding of metallurgical powder metallurgy HSS on the wear resistance was measured. Additionally, the cutting performance in a single point cutting tool machinability test at the configuration of the dry low-speed turning of steel was investigated. The results showed that deep cryogenic treatment itself, and in combination with nitriding, resulted in the reduction of the wear rate. The results of the single point cutting tool machinability test showed that deep cryogenic treated and nitrided HSS inserts performed worse than the classically heat-treated inserts and deep cryogenic treated HSS inserts exhibited approximately the same flank wear as the nitrided ones.