According to the fast development of portable electronic devices, their characteristics are inclined to miniature profile and lightweight. Nowadays, the wafer-level package (WLP) has been widely applied in portable electronic devices for its miniature profile and lightweight. It will become the mainstream trend later soon. The normal use of portable electronic devices brings low-frequency random vibrations to the electronic packages inside. Because of the increasing demand of these devices, the reliability of electronic packages subjected to repeated mechanical loads has become an important issue in the contemporary electronic packaging industry. In this paper both numerical and experimental studies were carried out to investigate the reliability life of Ultra-CSP under cyclic bending conditions. We perform four-point cyclic bending with various combinations of amplitudes and frequencies. Then, we do failure analysis in Ultra-CSP by observing the failure modes. A finite element model for the package is built up for dynamic as well as quasi-static analyses. Accumulated plastic work per bending cycle within the critical solder ball were calculated and together with the experimental results the parameters for the Coffin-Manson fatigue equation were fitted. Through finite element analysis we find that the solder ball which located in the corner has higher accumulated plastic work. Therefore, the crack in the solder ball grew more easily. Thus it lets package resistance rise to determine failure. It was observed from the bending experiments that the influence of frequencies on the fatigue life of the solder interconnects is inapparent. However, influence of amplitude is significant. From the results of both experiments and FEA, it was found that for this particular ultra-CSP specimen under cyclic bending conditions, the characteristic life was expressed as

Stiffness and strength models are derived for simply supported composite sandwich panels comprised of fibre-reinforced face sheets and polymer cores subject to symmetric four point bending and uniformly distributed loading. Optimal trajectories for minimum mass design are calculated using the models and situated on failure mechanism maps. A stiffness constraint is also derived to omit beam designs of excessive compliance. Analytical models were validated through an extensive series of experiments, considering beams comprised of GFRP face sheets with ROHACELL 51-IG and extruded polystyrene (EPS) polymer cores. An alternate loading fixture was used to simulate uniform pressure loads. In general, experiments were able to validate most analytical expressions for a range of experimental conditions. Though the predictions worked well with most beam cases, analytical models were noted to become unreliable for short or slender beams.

Stiffness and strength models are derived for simply supported composite sandwich panels comprised of fibre-reinforced face sheets and polymer cores subject to symmetric four point bending and uniformly distributed loading. Optimal trajectories for minimum mass design are calculated using the models and situated on failure mechanism maps. A stiffness constraint is also derived to omit beam designs of excessive compliance. Analytical models were validated through an extensive series of experiments, considering beams comprised of GFRP face sheets with ROHACELL 51-IG and extruded polystyrene (EPS) polymer cores. An alternate loading fixture was used to simulate uniform pressure loads. In general, experiments were able to validate most analytical expressions for a range of experimental conditions. Though the predictions worked well with most beam cases, analytical models were noted to become unreliable for short or slender beams.

Submitted by ALEMAR TORRES (eng.alemar@hotmail.com) on 2018-10-04T18:36:40Z No. of bitstreams: 4 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação_Alemar Pereira Torres.pdf: 3472665 bytes, checksum: 739d2a2cb37b6b4c6c7bae27196eb300 (MD5) Carta Encaminhamento_Autodepósito.pdf: 69827 bytes, checksum: 7b9ac0105db5d66ddd514b4063de104d (MD5) Ata de defesa.pdf: 494649 bytes, checksum: 6ef792196a9ddb6664cb8563e825accc (MD5) / Approved for entry into archive by PPGCEM Ciência e Engenharia de Materiais (ppgcem@ufam.edu.br) on 2018-10-09T17:07:33Z (GMT) No. of bitstreams: 4 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação_Alemar Pereira Torres.pdf: 3472665 bytes, checksum: 739d2a2cb37b6b4c6c7bae27196eb300 (MD5) Carta Encaminhamento_Autodepósito.pdf: 69827 bytes, checksum: 7b9ac0105db5d66ddd514b4063de104d (MD5) Ata de defesa.pdf: 494649 bytes, checksum: 6ef792196a9ddb6664cb8563e825accc (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-10-09T17:28:48Z (GMT) No. of bitstreams: 4 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação_Alemar Pereira Torres.pdf: 3472665 bytes, checksum: 739d2a2cb37b6b4c6c7bae27196eb300 (MD5) Carta Encaminhamento_Autodepósito.pdf: 69827 bytes, checksum: 7b9ac0105db5d66ddd514b4063de104d (MD5) Ata de defesa.pdf: 494649 bytes, checksum: 6ef792196a9ddb6664cb8563e825accc (MD5) / Made available in DSpace on 2018-10-09T17:28:48Z (GMT). No. of bitstreams: 4 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação_Alemar Pereira Torres.pdf: 3472665 bytes, checksum: 739d2a2cb37b6b4c6c7bae27196eb300 (MD5) Carta Encaminhamento_Autodepósito.pdf: 69827 bytes, checksum: 7b9ac0105db5d66ddd514b4063de104d (MD5) Ata de defesa.pdf: 494649 bytes, checksum: 6ef792196a9ddb6664cb8563e825accc (MD5) Previous issue date: 2018-06-18 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Biochar is a charcoal derived from the carbonization of biomass under a low oxygen atmosphere. Its origin is due to the study developed in the so-called "Indian black earth", which considerably improves the agricultural properties of a soil. In the work under study the influence of biochar as a participant of composites with soil and asphalt mixtures is analyzed by means of the four point bending test. We also compare these results regarding the responses of the formulations with the presence of native charcoal from the Amazon region. For this, prismatic formations of natural clay soil (SN), soil-charcoal (SCV), soil-biochar (SBC), asphalt concrete (CA), asphalt-charcoal concrete (CACV) and concrete asphalt-biochar (CABC). The results showed that the biomass, which participates in composites with the clay soil, improved the stiffness properties, with the purpose of its use in base and sub-base of pavements, culminating in higher values for complex module regarding the mixtures with charcoal . Allus asphaltic composites with biochar and charcoal were verified for both values of stiffness inferior to the standard asphalt concrete, considering average temperature of 25oC. However, for the 40oC temperature, representative of the surface of the pavements of the city of Manaus, these formulations proved to be more advantageous in comparison to the concrete reference, conceiving an alternative for the achievement of road systems with better performance in the Amazon region. / O biochar é um carvão vegetal oriundo da carbonização de biomassa sob baixa atmosfera de oxigênio. Sua origem deve-se ao estudo desenvolvido na chamada “terra preta de índio”, a qual melhora consideravelmente as propriedades agrícolas de um solo. No trabalho em pauta analisa-se a influência do biochar como partícipe de compósitos com solo e misturas asfálticas, por meio do ensaio de flexão a quatro pontos. Também se comparam tais resultados relativos as respostas das formulações com a presença do carvão vegetal nativo da região amazônica. Para tal moldaram-se os corpos de prova de formato prismático do solo argiloso natural (SN), solo-carvão vegetal (SCV), solo-biochar (SBC), concreto asfáltico (CA), concreto asfáltico-carvão vegetal (CACV) e concreto asfáltico-biochar (CABC). Os resultados registraram que o biocarvão, participante em compósitos com o solo argiloso, melhorou as propriedades de rigidez, com a finalidade de seu emprego em base e sub-base de pavimentos, culminando em maiores valores para módulo complexo respeitante as misturas com o carvão vegetal. Alusivo aos compósitos asfálticos com biochar e carvão vegetal, verificou-se para ambos valores de rigidez inferior ao concreto asfáltico padrão, considerando temperatura média de 25oC. No entanto, para a temperatura de 40oC, representativa da superfície dos pavimentos da cidade de Manaus, tais formulações se mostraram mais vantajosos frente ao concreto referência, concebendo uma alternativa para a consecução de sistemas viários com melhor desempenho na região Amazônica.

No description available.

The demand for an insert on composite sandwich structures to aid in the arrestment of face-core delamination is of great need. This research studies the use of a damage arrestment device (DAD) that connects the carbon fiber face sheets to the foam core to find whether an increase in the structural integrity of the sandwich beam results. Experimental analysis was employed to test the samples and was verified by a theoretical and finite element approach. The mechanical properties of LTM45/CF1803 pre-impregnated carbon fiber and Last-A-foam FR 6710 polyvinylchloride foam were experimentally analyzed using ASTM D3039 and ASTM D1621 standards respectively to verify the manufacturer’s data for the given material. With all the mechanical data, the effects of adding DAD keys to a delaminated composite sandwich beam were studied under a four-point bending test using ASTM standard D6272 and compared with non-delaminated beams to see if an increase in ultimate strength could be achieved. The initial delamination in the beams under consideration was one inch in length and located in between the loaded span of the beam. Two control beams were utilized for comparison: one with no defects, and another with a one inch delamination introduced at the face-core interface. The DAD keys were added in two different configurations to potentially stop the delamination propagation and increase the ultimate strength. In the first configuration DAD keys were added 0.25 inches on either side of the initial delamination in the transverse direction and provided a significant increase in strength over the delaminated control beam. The second configuration had a DAD key running along the longitudinal axis of the sandwich beam and resulted in a significant increase in ultimate strength over the delaminated control beam. After testing ten successful samples for each of the six different configurations, it was concluded that the addition of DAD keys in both configurations significantly increased the structural integrity of both the delaminated and non-delaminated control beams. With all the experimental data acquired, finite element models were created in COSMOS. The purpose of the finite element analysis was to validate the experimental results by comparing the deflections of the beam subjected to four-point bending during the experiment to the deflections found numerically. The deflections for the various DAD key configurations found in the experimental work were in agreement with the finite element results.

The use of timber in building structures is steadily increasing. cross laminated timber (CLT) is an engineered wood product made of an uneven number of layers of lamellas glued at an angle of 90 degrees to each other. This gives CLT high stiffness and strength to bending in all directions, and capability of taking load both in-plane and out-of-plane. Due to the large size of CLT elements, they allow for quick assembly of strong structures. Due to both economic and environmental reasons it is important for producers of CLT to optimize the use of the wood material by using the timber with higher stiffness and strength where it is most needed. This thesis is about evaluating the bending and shear stiffness of CLT elements, when used as plates, depending on the quality of wood used in the different layers. Four-point bending tests are carried out on elements of different compositions and a parametrized finite element model is created. Thus, the model is validated on the basis of experimental tests to evaluate the influence of different quality of different layers. The measured dynamic MoE proved to have good potential to be used as the longitudinal bending stiffness in an FE-model, with a deviation from the experimental tests of less than 1%. There is a strong correlation between the bending stiffness and bending strength of the plates. The effective rolling shear modulus in pine was calculated to be around 170 MPa for pine of dimension 40 x 195 mm2 . Grading the boards into two different classes used for different layers proved to increase the MoE of the plates by 11-17% for 3- and 5-layer CLT.

This study investigates the mechanical differences between old and newly produced slatted floors through a four-point bending test. To understand to what extent the actual environment has affected the slatted floors, the carbonation depth and corrosion will be examined. The tests showed no mechanical differences between slatted floors which had been in service for a certain amount of years and newly produces ones. Corrosion could be observed on some of the samples but it was not because of the carbonation process. When comparing the calculations of reinforced and pre-stressed concrete slatted floors, the result showed that the pre-stressed floor could carry up to double the load of what the reinforced slatted floor could. The conclusion of this study is, that the pre-stressed slatted floors will certainly hold for at least thirty years and will most likely hold for many years to come.

No description available.

No description available.