Impact Force Profile Research Articles

Effects of solder alloy constitutive relationships on impact force responses of package-level solder joints under ball impact test

The ball impact test was developed as a package-level measure for the board-level drop reliability of solder joints in the sense that it leads to fracturing of solder joints around intermetallics, similar to that from a board-level drop test. We investigated numerically the effects of constitutive relationships of solder alloy on transient structural responses of a single package-level solder joint subjected to ball impact testing. This study focused on the characteristics of the ascending part of the impact force profile. According to the piecewise linear stress-strain curve obtained for the Sn-4Ag-0.5Cu solder alloy, parametric studies were performed by varying either segmental moduli or characteristic stresses of the curve at fixed ratios, with regard to the lack of available rate-dependent material properties of solder alloys.

Two-step B-splines regularization method for solving an ill-posed problem of impact-force reconstruction

This paper presents a new method to accurately solve an ill-posed problem of the impact-force reconstruction. The method utilizes B-splines to approximate and to regularize the impact-force profile. The method computes the optimal solution in two steps: the first step estimates the global profile of the impact-force, and the second step refines the force obtained in the first step. The method provides a more accurate solution because it incorporates more prior information than existing methods. Three numerical experiments presented in this paper demonstrate effectiveness of the method.

Design Guideline for Ball Impact Test Apparatus

The ball impact test is developed as a package-level measure of the board-level reliability of solder joints in the sense that it leads to brittle intermetallic fracturing, similar to that from a board-level drop test. Following classical structural dynamics principles, the ball impact test process is analyzed to provide insights into transient characteristics of this particular test methodology. A design guideline for the ball impact test apparatus based on characteristics of the measured impact force profile is proposed.

Impact Fracture Behavior in Alumina Ceramic Plates

In this study, a bar impact test of low velocity was carried out to gain an insight into the damage mechanism and sequence induced in alumina plates during quasi-static impact conditions. An experimental setup which could measure directly the impact force applied to the specimen and supply a compressive pre-stress to the specimen by utilizing an long bar impact was devised. During the bar impact testing, the influence of the pre-stress applied to the specimen along the impact direction on the fracture behavior was investigated. The measured impact force profiles explained well the damage behavior induced in alumina plates. The application of higher pre-stress to the specimen led to less damage due to the suppression of radial cracks which was caused by the increase in the apparent stiffness of the plate. The observed results showed the following sequence in damage development: The development of cone crack at the impact region, the formation of radial cracks from the rear surface of plate depending on the plate thickness, and the occurrence of crushing or fragmentation within the cone envelope.

Impact Damage Behavior in Laminated Plates Using an Instrumented Long Bar

Laminated plates are widely used in structures such as automoblie and architectural glazing. In many cases the plate can be effectively used if it has properties including high-performance and low-specific weight. In this work. impact induced damage in glass/Al alloy laminated circular plates with an interlayer adhered of epoxy resin were investigated with an instrumented long bar impact under a state of biaxial bending stress using a ball-on-ring (BOR) bending fixture. In order to increase the damage tolerance of laminated plates, various material and geometric consideration are investigated to detamine their effects in maximizing absorbed impact energy. The parameters include the thickness of each layer and the material of the laminated plates. The measured impact force profiles can explain the damage behavior induced in laminated plates.

Impact strength measurement of spot welds

The impact strength of spot welds is a very important quality index in the automotive industry. However, impact testing is not routinely performed for weld quality testing because of its complexity, cost and relatively low reliability and repeatability. In this paper, the impact strength of steel spot welds was measured using a newly designed impact tester. Besides the impact energy of the welds, detailed impact process characteristics, such as impact force and displacement profiles, which may be important to understanding the impact performance of a weld for vehicle design and analysis, were also recorded. A brief description of the new impact tester and experimental results on welded joints using this device are presented. A sensitivity study of testing results to specimen size has been conducted, prior to experiments on the influence of weld size, shape and orientation on the impact strength of resistance spot-welded joints. Results of impact testing were also compared with those of static tensile shear tests. The correlation between weld attributes and impact performance also provides important information for the quality definition of spot welds. Initial tests using this impact tester show promise that it can be used to measure impact strength of a large variety of welds (spot welded, laser welded, brazed, etc.), and other joints (such as mechanical fasteners and adhesion).

An impact penetrometer for a landing spacecraft

The design, development and calibration of an impact force transducer or penetrometer, for use on the Huygens spacecraft scheduled to land on the surface of Saturn's satellite Titan, is described, The thumb-sized transducer employs a piezoelectric sensing element and is capable of working at cryogenic temperatures. Use of the sensor on a spacecraft imposes several reliability and safety constraints, as well as the desire to minimize mass (the sensor mass is 15 g). The impact force profile, measured at 10 kHz by the sensor, allows estimation of the density and cohesion of the surface material, and its particle size distribution. Sample profiles for terrestrial materials (sand, gravel and clay) are given.