A new computational procedure based on two Spring-Mass-Damper-Dashpot (SMDD) and Spring-Mass- Damper (SMD) models rePREsenting contact behavior between the impactor and the plate are PREsented to study the low velocity impact phenomenon of sandwich plates comprising of a transversely flexible core and laminated composite face-sheets. The interaction between the impactor and the plate is modeled with the help of a new system having three-degree of-freedom, consisting of spring-mass-damper-dashpot or spring mass- damper. The plate may be subjected to initial in-plane BIAXIAL normal and shear STRESSES along the edges of the plate. Impact is assumed to occur normally over the top or the bottom face-sheets, at arbitrary location. The boundary conditions of the top and the bottom face-sheets are independent. The effects of transverse flexibility of the core and structural damping of the plate are considered in the proposed models. Based on these models, the analytic functions describing the contact force, the transverse deflections of the impactor and the plate are derived. The effects of some parameters such as plate aspect ratio, boundary conditions, initial in-plane BIAXIAL STRESSES, and impact location are examined in details.

Accuracy in determination of mechanical properties in industrial parts is a major issue in engineering. Various methods have been introduced to estimate the mechanical properties of the industrial parts, and each has its own features and limitations. The PREsent research investigates the accuracy of Instrumented Indentation Technique (IIT) with Kim’s model in determining mechanical properties, including elastic modulus, yield stress, and work hardening of the A516 steel samples having surface STRESSES. To this end, some 3D simulations, using IIT on the steel sample with different surface stress state, were performed, and the method’s error in comparison to the initial assumed values were obtained. The results show that the surface STRESSES significantly affect the error in determining the materials’ properties, and the error in samples with tensile surface stress is more than that of samples with comPREssive one. To validate the results, some experimental samples with specified initial stress were PREpared, which measured mechanical properties by the IIT and then were compared with the tensile test results.

In this paper, the effect of PRE-STRESSES on the dynamic response of large fibre composite plates in the form of lamina and/or symmetric laminates subjected to low velocity transverse impact was studied using analytical procedure. PRE-STRESSES were considered in the form of tensile and comPREssive loads which are uni-axial as well as bi-axial types applied to the edges on mid-plane of the plate. Sveklo's contact law for anisotropic bodies was used. The effect of PRE-STRESSES was considered on contact force, contact time and central deflection of the plate. Using the same analytical method, the effect of uni-axial PRE-STRESSES applied along the fibres as well as perpendicular to the fibres and the effect of various ply sequences on the dynamic response of the plate subjected to transverse impact was studied.

To define failure under BIAXIAL stress, a three-dimensional surface in terms of two principal STRESSES and their orientation to the bed joints is required. This article describes a series of BIAXIAL comPREssion tests on full-scale brick specimens. Tests were performed on square unreinforced grouted brick masonry specimens with the principal comPREssive STRESSES oriented at 0 and 90 degree angles to the bed joints, and a failure surface was obtained in terms of these parameters. Test results indicated that the masonry strength under equal BIAXIAL comPREssion is higher by about 36% on average than that under uniaxial comPREssion; the influence of joint orientation is very in significant and negligible for these models.